Podcast
Questions and Answers
What is an advantage of using enumerations in programming?
What is an advantage of using enumerations in programming?
What is a characteristic of enum constants in an enumeration type?
What is a characteristic of enum constants in an enumeration type?
What is the purpose of the compareTo() method in an enumeration type?
What is the purpose of the compareTo() method in an enumeration type?
What is an example of a situation where an enumeration would be useful?
What is an example of a situation where an enumeration would be useful?
Signup and view all the answers
How is an enumeration type declared?
How is an enumeration type declared?
Signup and view all the answers
What is true about the built-in methods of an enumeration type?
What is true about the built-in methods of an enumeration type?
Signup and view all the answers
Where can an enumerated type be declared in Java?
Where can an enumerated type be declared in Java?
Signup and view all the answers
What is the purpose of the valueOf() method in the EnumDemo program?
What is the purpose of the valueOf() method in the EnumDemo program?
Signup and view all the answers
What is the data type of the pd variable in the main method?
What is the data type of the pd variable in the main method?
Signup and view all the answers
What is the purpose of the toUpperCase() method in the EnumDemo program?
What is the purpose of the toUpperCase() method in the EnumDemo program?
Signup and view all the answers
What is the purpose of the ordinal() method in the EnumDemo program?
What is the purpose of the ordinal() method in the EnumDemo program?
Signup and view all the answers
What is the purpose of the Period.values() method in the EnumDemo program?
What is the purpose of the Period.values() method in the EnumDemo program?
Signup and view all the answers
What does the toString() method of an enumeration constant return?
What does the toString() method of an enumeration constant return?
Signup and view all the answers
What is the purpose of the ordinal() method of an enumeration constant?
What is the purpose of the ordinal() method of an enumeration constant?
Signup and view all the answers
What does the valueOf() method of an enumeration type do?
What does the valueOf() method of an enumeration type do?
Signup and view all the answers
What is the purpose of the compareTo() method of an enumeration constant?
What is the purpose of the compareTo() method of an enumeration constant?
Signup and view all the answers
How can you declare a variable of an enumeration type?
How can you declare a variable of an enumeration type?
Signup and view all the answers
Where can you declare an enumerated type?
Where can you declare an enumerated type?
Signup and view all the answers
What is the position number of the grading period MIDTERM?
What is the position number of the grading period MIDTERM?
Signup and view all the answers
What is the output of the program if the enum Size is PARTY?
What is the output of the program if the enum Size is PARTY?
Signup and view all the answers
What is the main advantage of using enums in Java?
What is the main advantage of using enums in Java?
Signup and view all the answers
What is the term used to describe a data type that allows only appropriate behaviors?
What is the term used to describe a data type that allows only appropriate behaviors?
Signup and view all the answers
What is a class within another class called?
What is a class within another class called?
Signup and view all the answers
How many types of nested classes are there in Java?
How many types of nested classes are there in Java?
Signup and view all the answers
What is the primary reason for nesting a class inside another?
What is the primary reason for nesting a class inside another?
Signup and view all the answers
What is the HouseData class in the sample program?
What is the HouseData class in the sample program?
Signup and view all the answers
What is the purpose of the RealEstateListing class in the sample program?
What is the purpose of the RealEstateListing class in the sample program?
Signup and view all the answers
What is an anonymous class?
What is an anonymous class?
Signup and view all the answers
What is the purpose of the hData object in the sample program?
What is the purpose of the hData object in the sample program?
Signup and view all the answers
What is the benefit of packaging the classes together in the sample program?
What is the benefit of packaging the classes together in the sample program?
Signup and view all the answers
Study Notes
Enumerations
- An enumeration (enum) is a data type that contains a fixed set of constants.
- Enums are good to use when you already know all possibilities of the values or instances of the class.
- Enums can be declared on their own or within another class.
- Enums have built-in methods such as
compareTo()
,equals()
,toString()
,ordinal()
, andvalueOf()
. -
compareTo()
returns a negative integer if the calling object’s ordinal value is less than that of the argument, 0 if they are the same, and a positive integer if the calling object’s ordinal value is greater than that of the argument. -
equals()
returns true if its argument is equal to the calling object’s value. -
toString()
returns the name of the calling constant object. -
ordinal()
returns an integer that represents the constant’s position in the list of constants; the first position is 0. -
valueOf()
accepts a string parameter and returns an enumeration constant.
Creating Enums
- To create an enum, declare a type with the enum keyword, an identifier for the type, and a list of values called enum constants.
- An enumeration type such as
Period
is a class. - Its enum constants act like objects instantiated from the class, including having access to the methods of the class.
- Enums can be declared on their own or within another class but not within a method.
Example of Enums
-
public enum Period { PRELIM, MIDTERM, PREFINAL, FINAL; }
-
Period
is an enumeration type, andPRELIM
,MIDTERM
,PREFINAL
,FINAL
are enum constants.
Nested Classes
- In Java, you can create a class within another class and store them together; such classes are called nested classes.
- The containing class is the top-level class.
- There are four types of nested classes: static member class, non-static member class (inner class), local class, and anonymous class.
- The most common reason for nesting a class inside another is because the inner class is used only by the top-level class.
Example of Nested Classes
-
public class RealEstateListing { ... private class HouseData { ... } }
-
RealEstateListing
is the top-level class, andHouseData
is a private inner class.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge of enums in Java, including their use cases, declaration, and methods like ordinal() and compareTo.